A year after its initial release, the iPad tablet has made Apple the undisputed leader in the tablet space and created a whole new market niche, but strong competition is emerging, a prominent Apple iOS application developer said on Wednesday afternoon.

The iPad, which sold a reported 15 million units in 2010 after first shipping last April, broke ground on a new market, said developer Raven Zachary, president of Small Society, in a presentation at the Web 2.0 Expo conference in San Francisco. "There was no proven market at that time."

Although the device received some poor reviews in the press, people nonetheless lined up around the block in New York City to buy one, said Zachary, who also is founder of the iPhoneDevCamp developer conference for iOS application development. "Even Apple was not prepared for the demand of this platform."

Still, tablets have yet to make a major dent in enterprises. "Most of the enterprise users that I've spoken to buy them for their own benefit, bring them to the office, and use them as a work tool at their own expense," Zachary said. "I'm hearing [of] more and more buying tablets [for the enterprise], but it's not happening on a large scale."

Citing industry figures, Zachary said Apple had an 84 percent share of the tablet market, with Google's Android platform a distant second with 13 percent. But companies like Amazon, Motorola, Microsoft, Research in Motion, and HP are lining up to challenge Apple with their own devices.

Zachary anticipates that a possible Google Android-based tablet from Amazon has a great chance to battle Apple. "I think this really is the interesting opportunity that could really be a threat to Apple and iPad." Thanks to its Kindle reader device, Amazon already has factors weighing in its favor, such as custom hardware, excellent brand recognition, retail distribution, and content distribution rights with publications like the New York Times, Zachary said. "The Kindle is a common household electronic device, and that's going to mean a lot in terms of opportunity in the tablet space." Also, Amazon can afford low margins on its hardware because the company can make up the difference in digital content sales, where margins are much higher.

There is a vast growth opportunity for tablets, said Zachary. The growth opportunity "is huge," stretching into potential sales of hundreds of millions of units and quite possibly into the billions, he said. Retail distribution will be key to tablet distribution, according to Zachary. For himself, the iPad has served as a laptop replacement but not a computer replacement because of limitations like some websites not working on it.